Yes, accuracy in antigen tests seems to correlate very strongly with viral load (and presumably therefore with infectivity). This paper found 100% agreement with PCR for Ct 13-19.9 (massive viral load), all the way down to 8% agreement for Ct 30-35.
Ct (cycle time) measures how many amplification cycles were needed to detect nucleic acid. Lower Ct values indicate exponentially more nucleic acid than higher values, although Ct values are not standardized and can’t be directly compared between testing facilities.
Yes, accuracy in antigen tests seems to correlate very strongly with viral load (and presumably therefore with infectivity). This paper found 100% agreement with PCR for Ct 13-19.9 (massive viral load), all the way down to 8% agreement for Ct 30-35.
Ct (cycle time) measures how many amplification cycles were needed to detect nucleic acid. Lower Ct values indicate exponentially more nucleic acid than higher values, although Ct values are not standardized and can’t be directly compared between testing facilities.